STOCHASTIC SIMULATION OF SIZE VARIATION IN TURBOT - POSSIBLE CAUSES ANALYZED WITH AN INDIVIDUAL-BASED MODEL

Causes of size variation in a population of juvenile turbot were studi ed using an individual-based model (IBM). Each simulation started with 800 (divided into eight groups of 100 each) 120-day-old (posthatch) j uveniles and was run for 140 days, and the data gained from model simu lations compared directly with the result of a laboratory study with s ize-graded turbot. Stochastic growth with memory, which was included i n the models as an individual genetical growth rate variation, is impo rtant in explaining size variation, and the combination between indivi dual genetic growth rate and social interactions related to size-depen dent hierarchies also contributes to size variation. The use of size-d ependent growth rate alone fails to explain size variation, and is of little value in predicting size variation in turbot culture. Further, the results indicate formation of different types of size hierarchies for different sizes of juvenile turbot. (C) 1998 The Fisheries Society of the British Isles.